per·ni·cious 
/pɚˈnɪʃəs/ adjective
/pɚˈnɪʃəs/ adjective [more pernicious; most pernicious] formal : causing great harm or damage often in a way that is not easily seen or noticed
▪ More pernicious still has been the acceptance of the author's controversial ideas by the general public. ▪ the pernicious effects of jealousy ▪ She thinks television has a pernicious influence on our children.
▪ More pernicious still has been the acceptance of the author's controversial ideas by the general public. ▪ the pernicious effects of jealousy ▪ She thinks television has a pernicious influence on our children.
— per·ni·cious·ly adverb
